1. Field of the Invention
This invention relates to a chemical mechanical polishing apparatus and method for precisely and efficiently polishing a substrate, such as a wafer or the like.
2. Description of the Related Art
Recently, as semiconductor devices are going to have ultrafine patterns and high steps, it is requested to very precisely flatten the surface of a substrate, such as an SOI (silicon on insulator) substrate, a semiconductor wafer of Si, GaAs, InP or the like. Chemical mechanical polishing (CMP) apparatuses, such as one to be described below, are known as processing means for very precisely flattening the surface of a substrate, such as the above-described one or the like.
As shown in FIG. 13, a conventional chemical mechanical polishing apparatus includes a table 3 for rotating an object to be processed which can detachably hold a substrate 4, such as a wafer or the like, on a lower surface thereof, a polishing-tool rotating table 1 having an integrally-provided polishing pad 2, having a diameter larger than the diameter of the substrate 4, disposed below the rotating table 3 so as to face it, and supply nozzle 6 for supplying the upper surface of the polishing pad 2 with an abrasive (polishing slurry) 7. The substrate 4 is polished by providing the rotating table 3, holding the substrate 4, with a rotating movement indicated by an arrow B and a swinging movement indicated by a two-headed arrow C in a state of pressing the substrate 4 against the polishing pad 2. A shaft 5 rotates the rotating table 3 with a processing pressure in an axial direction indicated by a block arrow while rotating the upper surface of the polishing pad 2, provided as one body with the polishing-tool rotating table 1, in the direction of an arrow A with the abrasive (polishing slurry) 7.
In the above-described conventional approach, however, since the diameter of the polishing-tool rotating table having the polishing pad provided as one body therewith is larger than the diameter of the substrate, the following unsolved problems are present.
(1) The size of the polishing apparatus including the polishing-tool rotating table becomes large, and vibration occurs if the polishing-tool rotating table is rotated at too high a speed and hinders the very precise polishing of the surface to be polished of the substrate, serving as the object to be processed. Hence, the polishing-tool rotating table cannot be rotated at a high speed. As a result, the polishing speed (the amount of removal per unit time) cannot be increased, thereby increasing the processing cost.
(2) Since the substrate, serving as the object to be processed, is polished in a state in which the entire surface to be polished of the substrate contacts the polishing surface of the polishing pad, it is difficult to efficiently remove a local defect on the surface to be polished of the substrate if such a defect is present.